JP7079783B2 - Organic photoelectronic device - Google Patents

Description

The present invention relates to an organic photoelectronic device.

Conventionally, as a self-luminous element, an organic photoelectron element (organic electroluminescence element, hereinafter referred to as an organic EL element) is known. The organic EL element has a basic structure in which a plurality of types of layers such as a light emitting layer, an electron transport layer, and a hole transport layer are laminated between a pair of electrodes.

In the organic EL element, electrons supplied from a power source and holes are recombined in an internal light emitting layer to generate photons and emit light. In the field of organic EL devices, the "internal quantum efficiency", which is the ratio of "photons generated inside the device" to the "number of injected electrons", has reached nearly 100% through many years of research and development.

On the other hand, even in recent organic EL devices, the "external quantum efficiency", which is the ratio of "photons taken out to the outside of the device" to the "number of injected electrons", is only about 20 to 30%, and improvement is required. Has been done.

One of the causes of the low external quantum efficiency is considered to be internal reflection caused by the difference in refractive index of each layer constituting the organic EL element. As described above, the organic EL element has a plurality of types of layers in addition to the light emitting layer. These layers have different refractive indexes from each other. Therefore, it is conceivable that the light generated in the light emitting layer is reflected at the interface between the layers having different refractive indexes, and is attenuated or absorbed inside the device before being emitted to the outside of the device.

On the other hand, there is known an organic EL element in which nano-sized porous silica particles are contained in a charge transport layer to reduce the refractive index of the charge transport layer (see Patent Document 1). In the organic EL device described in Patent Document 1, it is expected that the reflection occurring at the interface between the charge transport layer and the layer in contact with the charge transport layer is suppressed, and the external quantum efficiency is improved.

International Publication No. 2013/108618

However, the higher the external quantum efficiency of the organic EL device is, the more preferable it is for the market demand for low power consumption and long life of the device. In this respect, there is room for improvement in the external quantum efficiency of the organic EL device described in Patent Document 1.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an organic optoelectronic device having improved external quantum efficiency, low power consumption, and long life.

In order to solve the above problems, one aspect of the present invention includes a substrate, an anode provided on the substrate, a cathode facing the anode, and a light emitting layer arranged between the anode and the cathode. The hole transport layer is provided between the light emitting layer and the anode in contact with the light emitting layer, and the hole transport layer contains an organic semiconductor material and a fluorine-containing polymer, and the light emitting layer. An organic photoelectron element in which the fluoropolymer is present is provided on the surface of the hole transport layer in contact with the anode.

In one aspect of the present invention, the hole transport layer may have a structure in which the internal refractive index is continuously and gradually increased from the light emitting layer toward the anode.

In one aspect of the present invention, the hole transport layer may be arranged between the anode and the anode, and may further have a hole injection layer containing a semiconductor material and a fluorine-containing polymer.

In one aspect of the present invention, the functional layer is further provided between the cathode and the light emitting layer, and the functional layer has at least one of an electron transport layer and an electron injection layer, and is a semiconductor material. It may be configured to include a fluorine-containing polymer.

According to the present invention, it is possible to provide an organic optoelectronic device having improved external quantum efficiency, low power consumption, and a long life.

It is sectional drawing which shows the organic EL element 1 which concerns on 1st Embodiment. It is sectional drawing which shows the organic EL element 2 which concerns on 2nd Embodiment. It is explanatory drawing of the organic EL element 3 which concerns on 3rd Embodiment. It is a schematic diagram which shows the process of manufacturing the hole transport layer 33 of the organic EL element 3. It is a schematic diagram which shows the process of manufacturing the hole transport layer 33 of the organic EL element 3. It is a schematic diagram which shows the process of manufacturing the hole transport layer 33 of the organic EL element 3. It is explanatory drawing explaining the change of the refractive index of a hole transport layer 33. It is explanatory drawing explaining the change of the refractive index of a hole transport layer 33.

The "external quantum efficiency" is a value expressed by the following equation.
η _EQE = γ × η _S × q × η _out
η _EQE : external quantum efficiency (%), γ: charge balance, η _S : emission exciter formation probability (%), q: emission quantum yield (%), η _out : light extraction efficiency (%).

"Weight average molecular weight" is a value measured by gel permeation chromatography (GPC). First, a PMMA standard sample having a known molecular weight is measured using GPC, and a calibration curve is created from the elution time and molecular weight of the peak top. Then, the fluorine-containing polymer is measured, the molecular weight is obtained from the calibration curve, and the weight average molecular weight is obtained. As the mobile phase solvent, 1,1,1,2,3,4,5,5,5-decafluoro-3-methoxy-2- (trifluoromethyl) pentane and hexafluoroisopropyl alcohol are used in a volume ratio of 85: The solvent mixed in 15 is used.
The "absorption coefficient of a layer containing a fluorine-containing polymer such as a hole transport layer (unit: cm ^-1 )" is an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation: UV-2450) for the layer on a quartz substrate. It is a value measured using.
"Inherent viscosity [η] (unit: dl / g)" is a Ubbelohde viscometer (Shibata Kagaku Co., Ltd .: viscometer Ubbelohde) using Asahiclin (registered trademark) AC2000 (manufactured by Asahi Glass Co., Ltd.) as a solvent at a measurement temperature of 30 ° C. ) Is the value measured by.
"Saturated vapor pressure (unit: Pa)" and "evaporation rate (unit: g / m ² sec)" are values measured by a vacuum differential heat balance (manufactured by Advance Riko Co., Ltd .: VPE-9000). It is charged in a cell with an inner diameter of 7 mm, heated at 2 ° C. per minute at a vacuum degree of 1 × 10 ^-3 Pa, and the evaporation rate at 300 ° C. is measured at g / m ² · sec. Uses the evaporation rate and the weight average molecular weight determined by the GPC measurement.
The "refractive index of the fluorine-containing polymer" is a value measured in accordance with JIS K 7142.
The "refractive index of the layer containing the fluorine-containing polymer such as the hole transport layer" is a value measured by the following method.
Using multi-incident angle spectroscopic ellipsometry (M-2000U), the incident angle of light is changed by 5 degrees in the range of 45 to 75 degrees with respect to the layer on the silicon substrate. Make a measurement. At each angle, the ellipsometry parameters Ψ and Δ are measured at intervals of approximately 1.6 nm in the wavelength range of 450 to 800 nm. Using the above measurement data, the dielectric function of the organic semiconductor is subjected to fitting analysis by the Cauchy model to obtain the refractive index of the layer with respect to light of each wavelength.

[First Embodiment]
Hereinafter, the organic photoelectronic device according to the first embodiment of the present invention will be described with reference to FIG. 1. In all the drawings below, the dimensions and ratios of each component are appropriately different in order to make the drawings easier to see.

FIG. 1 is a schematic cross-sectional view showing an organic photoelectron device (organic EL device) 1 of the present embodiment. The organic EL element 1 has a structure in which a substrate 10, an anode 11, a hole injection layer 12, a hole transport layer 13, a light emitting layer 14, an electron transport layer 15, an electron injection layer 16, and a cathode 17 are laminated in this order. There is. The organic EL element 1 of the present embodiment employs a bottom emission method in which the light L generated in the light emitting layer 14 is emitted to the outside via the anode 11 and the substrate 10.

(substrate)
The substrate 10 has light transmission. As the material for forming the substrate 10, an inorganic substance such as glass, quartz glass, or silicon nitride, or an organic polymer (resin) such as an acrylic resin or a polycarbonate resin can be used. Further, as long as it has light transparency, a composite material formed by laminating or mixing the above materials can also be used.

Further, the substrate 10 includes various wirings and driving elements (not shown) that are electrically connected to the organic EL element.

(anode)
The anode 11 is formed on the substrate 10 and supplies holes to the hole transport layer 13. Further, the anode 11 has a light transmittance that transmits light emitted from the light emitting layer 14. As the material for forming the anode 11, a conductive metal oxide such as ITO (Indium Tin Oxide: indium-doped tin oxide) or IZO (Indium Zinc Oxide: indium-doped zinc oxide) can be used. A semi-permeable membrane may be provided on the substrate 10 side of the anode 11.

The thickness of the anode 11 is not particularly limited, but is preferably 30 to 300 nm. The thickness of the anode 11 is, for example, 100 nm.

(Hole injection layer)
The hole injection layer 12 is formed between the anode 11 and the hole transport layer 13. The hole injection layer 12 has a function of facilitating the injection of holes from the anode 11 into the hole transport layer 13. The hole injection layer 12 does not have to be formed.

The hole injection layer 12 can be formed by using a known semiconductor material. Examples of such a material include the following semiconductor materials.
Metal oxides such as molybdenum oxide or tungsten oxide;
Organometallic complex materials such as copper phthalocyanine;
N, N'-di- (1-naphthyl) -N, N'-diphenylbenzidine (α-NPD), di- [4- (N, N-ditrill-amino) -phenyl] cyclohexane (TAPC), N ¹ , N ¹ , N ³ , N ³ -tetra-m-tolylbenzene-1,3-diamine (PDA), N, N'-diphenyl-N, N'-di (m-tolyl) benzidine (TPD), N , N'-diphenyl-N, N'-bis- [4- (phenyl-m-trill-amino) -phenyl] -biphenyl-4,4'-diamine (DNTPD), 4,4', 4''- Tris (3-methylphenylphenylamino) triphenylamine (m-MTDATA), 4,4', 4''-tris (N, N-diphenylamino) triphenylamine (TDATA), dipyrazino [2,3-f : 2', 3'-h] Kinoxalin-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), 9,9', 9''-triphenyl-9H, 9'H, 9''H-3,3': 6', 3''-tercarbazole (Tris-PCz), 4,4', 4''-tris (N, N-2-naphthylphenylamino) triphenylamine ( 2-TNATA) and other arylamine materials;
Polyaniline / dodecylbenzene sulfonic acid (PANI / DBSA), poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonate) (PEDOT / PSS), or polyaniline camphorsulfonic acid (PANI / CSA), polyaniline / Polymer semiconductor materials such as poly (4-styrene sulfonate) (PANI / PSS);
N- (diphenyl-4-yl) -9,9-dimethyl-N- (4- (9-phenyl-9H-carbazoyl-3yl) phenyl) -9H-fluorene-2-amine (hereinafter referred to as "HT211") ), HTM081 (Merck), HTM163 (Merck), HTM222 (Merck), NHT-5 (Novaled), NHT-18 (Novaled), NHT-49 (Novaled) , NHT-51 (manufactured by Novaled), NDP-2 (manufactured by Novaled), NDP-9 (manufactured by Novaled) and other commercially available products.
As the material for forming the hole injection layer 12, a commercially available product or a synthetic product may be used. Further, the material for forming the hole injection layer 12 may be used alone or in combination of two or more.

Further, the material for forming the hole injection layer 12 may include a dopant that facilitates charge transfer with the fluorine-containing polymer and the organic semiconductor material described later. Specific examples of dopants for hole injection materials include TCNQ, F4-TCNQ, _PPDN , TCNNQ, F6-TCNNQ, HAT-CN, HATNA, HATNA-Cl6, _{HATNA-F6, C 60 F 36} , F _16- . Examples thereof include organic dopants such as CuPc, NDP- ₂ (manufactured by Novaled) and NDP-9 (manufactured by Novaled), and inorganic dopants such as MoO ₃ , V2 O ₅ , WO ₃ , ReO ₃ and CuI. Only one kind of organic semiconductor material may be used, or two or more kinds may be used in combination. Further, only one type of the fluorine-containing polymer may be used, or two or more types may be used in combination.

The thickness of the hole injection layer 12 is not particularly limited, but is preferably 1 to 300 nm. The thickness of the hole injection layer 12 is, for example, 5 nm.

(Hole transport layer)
The hole transport layer 13 is formed on the hole injection layer 12. If there is no hole injection layer 12, the hole transport layer 13 is formed on the anode 11. The hole transport layer 13 has a function of satisfactorily transporting the holes injected from the anode 11 toward the light emitting layer 14. The hole transport layer 13 may be a single layer or a laminated body having a plurality of layers.

The hole transport layer 13 contains an organic semiconductor material and a fluorine-containing polymer. A fluorine-containing polymer is present on the surface of the hole transport layer 13 in contact with the light emitting layer 14.

Therefore, the hole transport layer 13 has a lower refractive index than the hole transport layer made of only an organic semiconductor material. The hole transport layer 13 preferably has a lower refractive index than the light emitting layer 14 in the wavelength range of 450 to 800 nm, and the refractive index of the hole transport layer 13 is preferably 1.60 or less, more preferably 1. It is .55 or less, more preferably 1.50 or less. The refractive index of the light emitting layer 14 can be adjusted by controlling the mixing ratio of the organic semiconductor material and the fluorine-containing polymer in the hole transport layer 13. Since the hole transport layer 13 has a low refractive index, the light extraction efficiency generated inside the organic EL element 1 is improved.

(Organic semiconductor material)
As the organic semiconductor material that is the material for forming the hole transport layer 13, a compound known as a hole transport material that receives and transports holes by injecting holes from the anode can be adopted.

As the hole transport material, an aromatic amine derivative can be preferably exemplified. Specific examples include the following α-NPD, TAPC, PDA, TPD, m-MTDATA and the like.

Other hole transport materials include N, N'-diphenyl-N, N'-bis- [4- (phenyl-m-trill-amino) -phenyl] -biphenyl-4,4'-diamine (DNTPD). , N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPB), 4,4', 4''-tris (N, N-diphenylamino) triphenylamine (TDATA), dipyrazino [2,3-f: 2', 3'-h] Kinoxalin-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), 9,9', 9''-triphenyl- 9H, 9'H, 9''H-3,3': 6', 3''-telcarbazole (Tris-PCz), 4,4', 4''-Tris (N, N-2-naphthylphenyl) Amino) triphenylamine (2-TNATA), 4,4', 4''-tri (9-carbazoyl) triphenylamine (TCTA), 2,2', 7,7'-tetrakis (N, N-diphenyl) Amino) -2,7-diamino-9,9'-spiro-TAD, 2,2', 7,7'-tetrakis (N, N-di-p-methoxyphenylamino) -9, Arylamine materials such as 9'-spiro-MeOTAD; polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonate) (PEDOT). / PSS), or polymer semiconductor materials such as polyaniline camphorsulfonic acid (PANI / CSA), polyaniline / poly (4-styrene sulfonate) (PANI / PSS); N- (diphenyl-4-yl) -9,9- Dimethyl-N- (4- (9-phenyl-9H-carbazoyl-3yl) phenyl) -9H-fluoren-2-amine (hereinafter referred to as "HT211"), HTM081 (manufactured by Merck), HTM163 (manufactured by Merck) , HTM222 (Merck), NHT-5 (Novaled), NHT-18 (Novaled), NHT-49 (Novaled), NHT-51 (Novaled) NDP-2 (Novaled) , NDP-9 (manufactured by Novaled) and the like on the market.
As the material for forming the hole transport layer 13, a commercially available product or a synthetic product may be used. Further, the material for forming the hole transport layer 13 may be used alone or in combination of two or more.

(Fluorine-containing polymer)
The fluorine-containing polymer contained in the charge injection layer and the charge transport layer of the present invention is a polymer containing a fluorine atom. In this embodiment, the oligomer is also included in the polymer. That is, the fluorine-containing polymer may be an oligomer.
From the viewpoint of the formation rate of a layer such as a hole transport layer, the strength of the layer and the surface roughness, the fluorine-containing polymer has an evaporation rate sufficient for practical use at a temperature below the temperature at which thermal decomposition of the fluorine-containing polymer occurs. It is preferable to have a saturated vapor pressure. The thermal decomposition start temperature of PTFE, which is a general fluorine-containing polymer, is about 400 ° C., and the thermal decomposition start temperature of Teflon (registered trademark) AF is 350 ° C. The evaporation rate of the fluorine-containing polymer according to the present embodiment at 300 ° C. is preferably 0.01 g / m ² sec or more, preferably 0.02 g / m ² sec or more. The saturated vapor pressure at 300 ° C. is preferably 0.001 Pa or more, more preferably 0.002 Pa or more. From this point of view, the fluorine-containing polymer is preferably a perfluoropolymer, which is considered to have a small intramolecular interaction. Further, a polymer having an aliphatic ring structure in the main chain, which is said to have low crystallinity, is more preferable. Here, the fact that the main chain has an aliphatic ring structure means that the fluoropolymer has an aliphatic ring structure (a ring structure that does not exhibit aromaticity) in the repeating unit and constitutes the aliphatic ring. It means that one or more carbon atoms make up the main chain.
In the present specification, the saturated vapor pressure (unit: Pa) is a value measured by a vacuum differential thermal balance (manufactured by Advance Riko Co., Ltd .: VPE-9000).

The weight average molecular weight of the fluorine-containing polymer (hereinafter referred to as “Mw”) is preferably 1,500 to 50,000, more preferably 3,000 to 40,000, still more preferably 5,000 to 30,000. .. When the weight average molecular weight is 1,500 or more, sufficient strength can be easily obtained when the layer is formed of the formed fluorine-containing polymer. On the other hand, when the weight average molecular weight is 50,000 or less, the vapor deposition source is heated to a high temperature, specifically, a temperature of more than 400 ° C. because it has a saturated vapor pressure that gives a practical layer formation rate (deposition rate). No need to heat up to. If the temperature of the vapor deposition source is too high, the main chain of the fluorinated polymer will be cleaved during the vapor deposition process, the fluorinated polymer will have a low molecular weight, the strength of the formed layer will be insufficient, and it will be derived from the decomposition product. Defects occur and it is difficult to obtain a smooth surface. In addition, it is assumed that molecules or ions generated by cleavage of the main chain and unintentionally mixed may affect the conductivity of the film and the emission lifetime of the organic EL element.
Therefore, when Mw is in the range of 1,500 to 50,000, a layer having sufficient strength and a smooth surface can be formed without causing cleavage of the main chain of the fluorine-containing polymer.
The “polydispersity” refers to the ratio of Mw to the number average molecular weight (hereinafter referred to as “Mn”), that is, Mw / Mn. From the viewpoint of quality stability in the formed layer, the polydispersity (molecular weight distribution) (Mw / Mn) of the fluorine-containing polymer is preferably small, preferably 2 or less. The theoretical lower limit of the polydispersity is 1. Examples of the method for obtaining a fluoropolymer having a small degree of polydispersity include a method for performing controlled polymerization such as living radical polymerization, a molecular weight fraction purification method using size exclusion chromatography, and a molecular weight fraction purification method by sublimation purification. Of these methods, it is preferable to perform sublimation purification in consideration of the stability of the vapor deposition rate when the vapor deposition method is applied to the formation of the layer.
In the present specification, Mw and Mn are values measured by gel permeation chromatography (GPC).
It is preferable that the glass transition point (Tg) of the fluorine-containing polymer is high because the reliability of the obtained device is high. Specifically, the glass transition point is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and particularly preferably 100 ° C. or higher. The upper limit is not particularly limited, but 350 ° C is preferable, and 300 ° C is more preferable.

A perfluoropolymer having a fluorine-containing aliphatic ring structure in the main chain is also a perfluoropolymer consisting of only repeating units formed by cyclizing and polymerizing perfluoro (3-butenyl vinyl ether) (also known as polyperfluoro (3-butenyl vinyl ether)). In the case of), the intrinsic viscosity [η] is preferably 0.01 to 0.14 dl / g, more preferably 0.02 to 0.1 dl / g, and 0.02 to 0. It is particularly preferable that it is 08 dl / g. When [η] is 0.01 dl / g or more, the molecular weight of the fluorine-containing polymer is relatively large, and sufficient strength can be easily obtained in the formed layer. On the other hand, when [η] is 0.14 dl / g or less, the molecular weight of the fluorine-containing polymer is relatively small, and it has a saturated vapor pressure that gives a practical film formation rate.
In the present specification, the intrinsic viscosity [η] (unit: dl / g) is an Ubbelohde viscometer (manufactured by Shibata Kagaku Co., Ltd .:) using Asahiclin (registered trademark) AC2000 (manufactured by Asahi Glass Co., Ltd.) as a solvent at a measurement temperature of 30 ° C. It is a value measured by a viscometer Ubbelohde).

The upper limit of the refractive index of the fluorine-containing polymer at a wavelength of 450 nm to 800 nm is preferably 1.5, more preferably 1.4. If the refractive index is 1.5 or less, the refractive index of the layers such as the charge injection layer and the charge transport layer obtained by mixing with the organic semiconductor material is up to about 1.55, which is the same level as the refractive index of the glass substrate or the like. It is preferable because it can be lowered and the light extraction efficiency is improved. On the other hand, the theoretical lower limit of the refractive index is 1.0.
The refractive index of an organic semiconductor material is generally about 1.7 to 1.8. If a fluorine-containing polymer having a refractive index of 1.5 or less is mixed with such a general organic semiconductor material, the refractive index of the obtained charge injection layer, charge transport layer, or the like can be lowered. The refractive index of the charge injection layer and the charge transport layer is lowered, and the charge injection layer, the electrode adjacent to the charge transport layer, the glass substrate, etc. (the refractive index of soda glass and quartz glass is about 1.51 to each in the visible light region. Closer to the index of refraction of 1.53, about 1.46 to 1.47), the total reflection that occurs at the interface between the charge injection layer or charge transport layer and the electrode or glass substrate can be avoided. Light extraction efficiency is improved.

Examples of the fluorine-containing polymer include the following polymers (1) and (2).
Polymer (1): A fluorine-containing polymer having no aliphatic ring in the main chain and having a unit derived from a fluoroolefin (hereinafter, also referred to as “fluoroolefin unit”).
Polymer (2): A fluorine-containing polymer having an aliphatic ring in the main chain.

≪Polymer (1) ≫
The polymer (1) may be a homopolymer of a fluoroolefin or a copolymer of a fluoroolefin and another monomer copolymerizable with the fluoroolefin.

Examples of the fluoroolefin include tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, vinylfluoride, perfluoroalkylethylene (those having a perfluoroalkyl group having 1 to 10 carbon atoms, etc.), and perfluoro (alkyl vinyl ether). , Trifluoroethylene and the like.
Among the examples, tetrafluoroethylene, hexafluoropropylene, and perfluoro (alkyl) in which all hydrogen atoms bonded to carbon atoms are replaced with fluorine because the refractive index of the charge injection layer and the charge transport layer can be easily lowered. Vinyl ether) is preferred.

Examples of other monomers copolymerizable with the fluoroolefin include vinyl ethers, vinyl esters, aromatic vinyl compounds, allyl compounds, acryloyl compounds, and methacryloyl compounds.
When the polymer (1) is a copolymer, the proportion of the unit derived from the fluoroolefin is preferably 20 mol% or more, more preferably 40 mol% or more, still more preferably 80 mol% or more.

The functional group at the end of the main chain of the polymer (1) is preferably a functional group having low reactivity. Examples of the functional group having low reactivity include an alkoxycarbonyl group and a trifluoromethyl group.

As the polymer (1), a synthesized polymer may be used, or a commercially available product may be used.
Examples of the polymer (1) include the following fluorine-containing polymers.
Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer ((Asahi Glass Co., Ltd .: Fluon (registered trademark) PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoro Ethylene / perfluoro (alkyl vinyl ether) / hexafluoropropylene copolymer (EPA), ethylene-tetrafluoroethylene copolymer (manufactured by Asahi Glass Co., Ltd .: Fluon (registered trademark) ETFE), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE) and the like.
Among the examples, polytetrafluoroethylene (PTFE) in which all hydrogen atoms or chlorine atoms bonded to carbon atoms are replaced with fluorine because the refractive index of the charge injection layer and the charge transport layer is likely to be lowered, Tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoro (alkyl vinyl ether) -hexafluoropropylene copolymer (EPA) preferable.
The polymer (1) can be produced by using a known method.
As the polymer (1), a synthesized polymer may be used, or a commercially available product may be used.

≪Polymer (2) ≫
The polymer (2) is a fluorine-containing polymer having an aliphatic ring in the main chain.
The "fluorine-containing polymer having an aliphatic ring structure in the main chain" means that the fluoropolymer has a unit having an aliphatic ring structure and one or more carbon atoms constituting the aliphatic ring are present. It means that it is a carbon atom that constitutes the main chain. The aliphatic ring may be a ring having a hetero atom such as an oxygen atom.
The "main chain" of a polymer means a chain of carbon atoms derived from two carbon atoms constituting the polymerizable double bond in a monoene polymer having a polymerizable double bond, and can be cyclized and polymerized. In the cyclized polymer of diene, it refers to a chain of carbon atoms derived from four carbon atoms constituting two polymerizable double bonds. In a copolymer of a monoene and a diene capable of cyclization polymerization, a main chain is composed of the above two carbon atoms of the monoene and the above four carbon atoms of the diene.
Therefore, in the case of a monoene polymer having an aliphatic ring, one carbon atom constituting the ring skeleton of the aliphatic ring or two adjacent carbon atoms constituting the ring skeleton form a polymerizable double bond carbon. It is a polymer of monoene having a structure that is an atom. In the case of a diene cyclization polymer capable of cyclization polymerization, as described later, 2 to 4 of the four carbon atoms constituting the two double bonds are carbon atoms constituting the aliphatic ring.

The number of atoms constituting the ring skeleton of the aliphatic ring in the polymer (2) is preferably 4 to 7, and particularly preferably 5 to 6. That is, the aliphatic ring is preferably a 4- to 7-membered ring, and particularly preferably a 5- to 6-membered ring. When a hetero atom is used as an atom constituting the ring of the aliphatic ring, examples of the hetero atom include an oxygen atom and a nitrogen atom, and an oxygen atom is preferable. The number of heteroatoms constituting the ring is preferably 1 to 3, and more preferably 1 or 2.
The aliphatic ring may or may not have a substituent. "May have a substituent" means that the substituent may be bonded to an atom constituting the ring skeleton of the aliphatic ring.

It is preferable that the hydrogen atom bonded to the carbon atom constituting the aliphatic ring of the polymer (2) is replaced with a fluorine atom. Further, when the aliphatic ring has a substituent and the substituent has a hydrogen atom bonded to a carbon atom, it is preferable that the hydrogen atom is substituted with a fluorine atom. Examples of the substituent having a fluorine atom include a perfluoroalkyl group, a perfluoroalkoxy group, and = CF ₂ .
As the aliphatic ring in the polymer (2), since the refractive index of the charge injection layer and the charge transport layer is likely to be lowered, all of the hydrogen atoms bonded to the carbon atom including the substituent are contained in the perfluoroaliphatic ring. Aliphatic rings substituted with fluorine atoms) are preferred.

Examples of the polymer (2) include the following polymers (21) and (22).
Polymer (21): A fluorinated polymer having a unit derived from a fluorinated cyclic monoene,
Polymer (22): A fluorine-containing polymer having a unit formed by cyclization polymerization of a fluorine-containing diene (hereinafter, also simply referred to as “fluorine-containing diene”) capable of cyclization polymerization.

Fluorine polymer (21):
The "fluorine-containing cyclic monoene" is a fluorine-containing monomer having one polymerizable double bond between carbon atoms constituting the aliphatic ring, or a carbon atom constituting the aliphatic ring and the outside of the aliphatic ring. It is a fluorine-containing monomer having one polymerizable double bond with a carbon atom.
As the fluorine-containing cyclic monoene, the following compound (1) or compound (2) is preferable.

［式中、Ｘ^１、Ｘ^２、Ｘ^３、Ｘ^４、Ｙ^１およびＹ^２は、それぞれ独立に、フッ素原子、エーテル性酸素原子（－Ｏ－）を含んでいてもよいペルフルオロアルキル基、またはエーテル性酸素原子を含んでいてもよいペルフルオロアルコキシ基である。Ｘ^３およびＸ^４は相互に結合して環を形成してもよい。］

[In the formula, X ¹ , X ² , X ³ , X ⁴ , Y ¹ and Y ² , respectively, may independently contain a fluorine atom, an etheric oxygen atom (—O—), or a perfluoroalkyl group. It is a perfluoroalkoxy group that may contain an ethereal oxygen atom. X ³ and X ⁴ may be coupled to each other to form a ring. ]

The perfluoroalkyl groups in X ¹ , X ² , X ³ , X ⁴ , Y ¹ and Y ² preferably have 1 to 7 carbon atoms, and particularly preferably 1 to 4 carbon atoms. The perfluoroalkyl group is preferably linear or branched, and particularly preferably linear. Specific examples thereof include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group and the like, and a trifluoromethyl group is particularly preferable.
Examples of the perfluoroalkoxy group in X ¹ , X ² , X ³ , X ⁴ , Y ¹ and Y ² include those in which an oxygen atom (—O—) is bonded to the perfluoroalkyl group, and a trifluoromethoxy group is particularly preferable. preferable.

In formula (1), X ¹ is preferably a fluorine atom.
X ² is preferably a fluorine atom, a trifluoromethyl group, or a perfluoroalkoxy group having 1 to 4 carbon atoms, and particularly preferably a fluorine atom or a trifluoromethoxy group.
It is preferable that X ³ and X ⁴ are independently a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms, and particularly preferably a fluorine atom or a trifluoromethyl group.
X ³ and X ⁴ may be coupled to each other to form a ring. The number of atoms constituting the ring skeleton of the ring is preferably 4 to 7, and particularly preferably 5 to 6.
Preferred specific examples of the compound (1) include compounds (1-1) to (1-5).

In the formula (2), Y ¹ and Y ² are each independently preferably a fluorine atom, a perfluoroalkyl group having 1 to 4 carbon atoms or a perfluoroalkoxy group having 1 to 4 carbon atoms, and a fluorine atom or a trifluoromethyl group is preferable. Especially preferable.
Preferred specific examples of the compound (2) include compounds (2-1) and (2-2).

The polymer (21) may be a homopolymer of the above-mentioned fluorine-containing cyclic monoene, or may be a copolymer of another monomer copolymerizable with the fluorine-containing cyclic monoene.
However, the ratio of the unit derived from the fluorine-containing cyclic monoene to all the units in the polymer (21) is preferably 20 mol% or more, more preferably 40 mol% or more, still more preferably 100 mol%.
Other monomers copolymerizable with the fluorine-containing cyclic monoene include, for example, fluorine-containing diene, a monomer having a reactive functional group on the side chain, tetrafluoroethylene, chlorotrifluoroethylene, and perfluoro (methyl vinyl ether). And so on.
Examples of the fluorine-containing diene include those similar to those mentioned in the description of the polymer (22) described later. Examples of the monomer having a reactive functional group in the side chain include a monomer having a polymerizable double bond and a reactive functional group. Examples of the polymerizable double bond include CF ₂ = CF-, CF ₂ = CH-, CH ₂ = CF-, CFH = CF-, CFH = CH-, CF ₂ = C-, CF = CF-and the like. .. Examples of the reactive functional group include those similar to those mentioned in the description of the polymer (22) described later.
The polymer obtained by the copolymerization of the fluorine-containing cyclic monoene and the fluorine-containing diene is the polymer (21).

Polymer (22):
The "fluorine-containing diene" is a fluorinated monomer having two polymerizable double bonds and a fluorine atom and capable of cyclization polymerization. As the polymerizable double bond, a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group are preferable. As the fluorine-containing diene, the following compound (3) is preferable.
CF ₂ = CF-Q-CF = CF ₂ ... (3).
In the formula (3), Q may contain an ethereal oxygen atom, and a part of the fluorine atom may be substituted with a halogen atom other than the fluorine atom. The number of carbon atoms is 1 to 5, preferably 1 to 3. Is a perfluoroalkylene group which may have a branch. Examples of the halogen atom other than fluorine include a chlorine atom and a bromine atom.
Q is preferably a perfluoroalkylene group containing an ethereal oxygen atom. In that case, the etheric oxygen atom in the perfluoroalkylene group may be present at one end of the perfluoroalkylene group, may be present at both ends of the perfluoroalkylene group, and may be present at both ends of the perfluoroalkylene group. It may exist between carbon atoms. From the viewpoint of cyclization polymerizability, it is preferable that an ethereal oxygen atom is present at one end of the perfluoroalkylene group.

Specific examples of the compound (3) include the following compounds.
CF ₂ = CFOCF ₂ CF = CF ₂ ,
CF ₂ = CFOCF (CF ₃ ) CF = CF ₂ ,
CF ₂ = CFOCF ₂ CF ₂ CF = CF ₂ ,
CF ₂ = CFOCF ₂ CF (CF ₃ ) CF = CF ₂ ,
CF ₂ = CFOCF (CF ₃ ) CF ₂ CF = CF ₂ ,
CF ₂ = CFOCFClCF ₂ CF = CF ₂ ,
CF ₂ = CFOCCl ₂ CF ₂ CF = CF ₂ ,
CF ₂ = CFOCF ₂ OCF = CF ₂ ,
CF ₂ = CFOC (CF ₃ ) ₂ OCF = CF ₂ ,
CF ₂ = CFOCF ₂ CF (OCF ₃ ) CF = CF ₂ ,
CF ₂ = CFCF ₂ CF = CF ₂ ,
CF ₂ = CFCF ₂ CF ₂ CF = CF ₂ ,
CF ₂ = CFCF ₂ OCF ₂ CF = CF ₂ .

Examples of the unit formed by the cyclization polymerization of the compound (3) include the following units (3-1) to (3-4).

The polymer (22) may be a homopolymer of a fluorine-containing diene, or may be a copolymer of another monomer copolymerizable with the fluorine-containing diene.
Examples of other monomers copolymerizable with the fluorine-containing diene include monomers having a reactive functional group in the side chain, tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether) and the like.

As a specific example of the polymer (22), for example, the following formula (3-1-) obtained by cyclization polymerization of CF ₂ = CFOCF ₂ CF ₂ CF = CF ₂ (perfluoro (3-butenyl vinyl ether)) is carried out. Examples thereof include the polymer represented by 1).
Hereinafter, perfluoro (3-butenyl vinyl ether) is referred to as "BVE".

However, in the equation (3-1-1), p is an integer of 5 to 1,000.
p is preferably an integer of 10 to 800, and particularly preferably an integer of 10 to 500.

The functional group at the end of the main chain of the polymer (2) is preferably a functional group having low reactivity. Examples of the functional group having low reactivity include an alkoxycarbonyl group and a trifluoromethyl group.

As the polymer (2), a synthesized polymer may be used, or a commercially available product may be used.
Specific examples of the polymer (2) include a BVE cyclized polymer (manufactured by Asahi Glass Co., Ltd .: Cytop (registered trademark)) and a tetrafluoroethylene / perfluoro (4-methoxy-1,3-dioxol) copolymer (Solbay). Hyflon (registered trademark) AD), tetrafluoroethylene / perfluoro (2,2-dimethyl-1,3-dioxol) copolymer (Dupont: Teflon (registered trademark) AF), perfluoro (4-methyl) -2-Methylene-1,3-dioxolane) polymer (MMD polymer) is preferable.

In the present invention, the fluorine-containing polymer is preferably the polymer (2), more preferably the polymer (22), and is obtained by cyclizing and polymerizing BVE, according to the formula (3-1-1). The fluorine-containing polymer represented by is particularly preferable.

The material for forming the hole transport layer 13 may include a dopant that facilitates charge transfer with the above-mentioned fluorine-containing polymer and organic semiconductor material. Specific examples of dopants for hole transport materials include TCNQ, F4-TCNQ, _PPDN , TCNNQ, F6-TCNNQ, HAT-CN, HATNA, HATNA-Cl6, _{HATNA-F6, C 60 F 36} , F _16- . Examples thereof include organic dopants such as CuPc, NDP- ₂ (manufactured by Novaled) and NDP-9 (manufactured by Novaled), and inorganic dopants such as MoO ₃ , V2 O ₅ , WO ₃ , ReO ₃ and CuI. However, only one type of organic semiconductor material may be used, or two or more types may be used in combination. Further, only one type of the fluorine-containing polymer may be used, or two or more types may be used in combination.

In the material for forming the hole transport layer 13, the volume ratio of the fluorine-containing polymer to the organic semiconductor material is preferably 70:30 to 5:95, and more preferably 60:40 to 20:80. When the volume ratio of the fluorine-containing polymer to the organic semiconductor material is in the above range, the refractive index of the obtained hole transport layer 13 is lowered to the same level as the refractive index of the glass substrate or the like, and light is extracted from the organic EL element. This is preferable because it improves efficiency.

Such a hole transport layer 13 can be formed by a known dry coat method or wet coat method.

When the organic semiconductor material to be used is a polymer material, a known wet coating method may be adopted for forming the hole transport layer 13. Examples of the wet coating method include an inkjet method, a cast coating method, a dip coating method, a bar coating method, a blade coating method, a roll coating method, a gravure coating method, a flexographic coating method, and a spray coating method. When the wet coat method is adopted, a solution or a dispersion liquid in which the organic semiconductor material to be used and the fluorine-containing polymer are mixed at a desired ratio may be prepared, and a film may be formed by any of the above methods.

When the organic semiconductor material used is a small molecule material, a known dry coat method may be adopted for forming the hole transport layer 13. The dry coat method is preferable because it is easy to form a film of the fluorine-containing polymer and the organic semiconductor material at a uniform mixing ratio.

Examples of the dry coating method include a resistance heating vapor deposition method, an electron beam vapor deposition method, and a physical vapor deposition method such as a sputtering method. The hole transport layer 13 formed by the physical vapor deposition method is a physical vapor deposition layer. When the material for forming the hole transport layer 13 is a small molecule material, it is highly probable that the hole transport layer 13 is a physically vapor-deposited layer. Of these, the resistance heating vapor deposition method is preferable because it is easy to form a film without decomposing the organic semiconductor and the fluorine-containing polymer, and the resistance heating includes a step of co-depositing the fluorine-containing polymer and the organic semiconductor material. The co-deposited method is particularly preferable.

The vapor deposition rate in the co-deposited film (the total vapor deposition rate of the fluorine-containing polymer and the organic semiconductor material) is not particularly limited, but is preferably 0.001 to 10 nm / s. At this time, the mixing ratio can be controlled by the vapor deposition rate ratio of the fluorine-containing polymer and the organic semiconductor material.

The hole transport layer 13 preferably has an absorption coefficient of 5000 cm ^-1 or less in a wavelength range of 450 nm to 800 nm, more preferably 1000 cm ^-1 or less, and particularly having no absorption band in the above wavelength range. preferable.

When the absorption coefficient of each layer constituting the hole transport layer 13 exceeds 5000 cm ^-1 , when light passes through the hole transport layer having a thickness of 100 nm once, it is 5% compared to the case where the total amount of light before passing is 100%. Light is absorbed. Inside the organic EL element, the loss due to the absorption of light when passing through the hole transport layer 13 is accumulated due to the multiple interference of light. Therefore, light absorption when passing through the hole transport layer is a factor that greatly reduces the light extraction efficiency. It is extremely important to use a hole transport layer having sufficiently small light absorption so as not to impair the luminous efficiency of the organic electroluminescent device. Since the luminous efficiency of the organic EL element is not impaired, the energy utilization efficiency is increased, and as a result of suppressing heat generation due to light absorption, the device life is extended.

The thickness of the hole transport layer 13 is not particularly limited, but is preferably 10 nm to 350 nm, more preferably 20 nm to 300 nm.

(Light emitting layer)
The light emitting layer 14 is formed in contact with the hole transport layer 13. In the light emitting layer 14, the holes injected from the anode 11 and the electrons injected from the cathode 17 are recombined to emit photons and emit light. The emission wavelength at that time is determined according to the material for forming the light emitting layer 14.

As the material for forming the light emitting layer 14, known materials such as a fluorescent material, a thermal activated delayed fluorescent (TADF) material, and a phosphorescent material can be adopted. For example, as the material for forming the light emitting layer 14, (E) -2- (2- (4- (dimethylamino) styryl) -6-methyl-4H-pyran-4-iriden) malononitrile (DCM), 4-( Dicyanomethylene) -2-methyl-6-juloridyl-9-enyl-4H-pyran (DCM ₂ ), rubrene, Polymer6, Ir (ppy) ₃ , (ppy) ₂ Ir (acac) and other light emitting dopant materials, 4, Phosphorescent host materials such as 4'-bis (9H-carbazole-9-yl) biphenyl (CBP), 3,3'-di (9H-carbazole-9-yl) -1,1'-biphenyl (mCBP), Examples include, but are not limited to, fluorescent host materials such as ADN and Alq ₃ and polymer materials such as polyphenylene vinylene (PPV) and MEH-PPV. The material for forming the light emitting layer 14 may be used alone or in combination of two or more, and is appropriately selected according to a desired emission wavelength. The refractive index of the light emitting layer 14 is 1.65 to 1.90 in the wavelength range of 450 nm to 800 nm, and is 1.70 to 1.80 in the wavelength range of 600 nm, for example.
The thickness of the light emitting layer 14 is not particularly limited, but is preferably 10 to 30 nm. The thickness of the light emitting layer 14 is, for example, 15 nm.

(Electron transport layer)
The electron transport layer 15 is formed in contact with the light emitting layer 14. The electron transport layer 15 has a function of satisfactorily transporting electrons injected from the cathode 17 toward the light emitting layer 14. The electron transport layer 15 does not have to be formed.

As the material for forming the electron transport layer 15, known materials can be adopted. For example, as the material for forming the electron transport layer 15, the following Alq ₃ , PBD, TAZ, BND, OXD-7, 2,2', 2''-(1,3,5-benzinetriyl) -tris ( 1-Phenyl-1-H-benzimidazole) (TPBi) can be mentioned. In addition, examples of the material for forming the electron transport layer 15 include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), t-Bu-PBD, and a siror derivative. The material for forming the electron transport layer 15 is not limited to these. The electron transport layer 15 may contain a material common to the light emitting layer 14.

Further, the electron transport layer 15 may contain a fluorine-containing polymer described later. In this case, the electron transport layer 15 preferably has a lower refractive index than the light emitting layer 14 in the wavelength range of 450 to 800 nm.

The thickness of the electron transport layer 15 is not particularly limited, but is preferably 30 to 200 nm. The thickness of the electron transport layer 15 is, for example, 60 nm.

(Electron injection layer)
The electron injection layer 16 is provided between the cathode 17 and the electron transport layer 15. When the electron transport layer 15 is not provided, the electron injection layer 16 is provided between the cathode 17 and the light emitting layer 14. The electron injection layer 16 has a function of facilitating the injection of electrons from the cathode 17 into the electron transport layer 15 or the light emitting layer 14. As a material for forming the electron injection layer 16, a generally known material can be used. Specific examples include, but are not limited to, inorganic compounds such as LiF, Cs ₂ CO ₃ , and CsF, and the following Alq ₃ , PBD, TAZ, BND, OXD-7, and the like.

Further, the electron injection layer 16 may contain a fluorine-containing polymer described later. In this case, the electron injection layer 16 preferably has a lower refractive index than the light emitting layer 14 in the wavelength range of 450 to 800 nm.
The electron injection layer 16 does not have to be formed.

The thickness of the electron injection layer 16 is not particularly limited, but is preferably 0.5 to 2 nm. The thickness of the electron injection layer 16 is, for example, 1 nm.

(cathode)
The cathode 17 is formed in contact with the electron injection layer 16. In the absence of the electron injection layer 16, the cathode 17 is formed in contact with the electron transport layer 15, and in the absence of the electron injection layer and the electron transport layer 15, the cathode 17 is formed in contact with the light emitting layer 14. To. The cathode 17 has a function of injecting electrons into the electron injection layer 16, the electron transport layer 15, or the light emitting layer 14. As the material for forming the cathode 17, a known material can be adopted. For example, examples of the material for forming the cathode 17 include an MgAg electrode and an Al electrode. A buffer layer such as LiF may be formed on the surface of the Al electrode.

Further, the cathode 17 has a function as a reflective film that reflects the light L that is isotropically emitted in the light emitting layer 14 and directs the light L toward the anode 11.

The thickness of the cathode 17 is not particularly limited, but is preferably 30 to 300 nm. The thickness of the cathode 17 is, for example, 100 nm.

The organic EL element 1 has the following effects due to the above configuration.

First, the hole transport layer 13 contains a fluorine-containing polymer, and the refractive index is set to be lower than that in the case where the hole transport layer 13 does not contain the fluorine-containing polymer, whereby the light extraction efficiency is achieved. Is improved.

Secondly, since the light emitting layer 14 and the hole transport layer 13 having a relatively lower refractive index than the light emitting layer 14 are in contact with each other, the reflection loss inside the element is reduced and the light extraction efficiency is improved. ..

When light is incident on the interface between two layers with different refractive indexes, part of the light is refracted and the rest is reflected. Further, when light is incident from a layer having a large refractive index toward a layer having a small refractive index, total reflection may occur at the interface between the two layers depending on the angle of incidence.

When the light generated in the light emitting layer 14 is reflected at the interface 14a between the light emitting layer 14 and the hole transport layer 13 shown in FIG. 1, the probability that the reflected light is attenuated inside the organic EL element increases. As a result, the light extraction efficiency is lowered.

Reflection at such an interface is more likely to occur as the difference in refractive index between the two layers in contact with each other is larger. Therefore, in order to suppress interfacial reflection, it is preferable to reduce the difference in refractive index between layers.

Considering this way, when the hole transport layer contains an organic semiconductor material and a fluorine-containing polymer, the hole transport layer that does not contain the fluorine-containing polymer at the position in contact with the light emitting layer 14 (hereinafter, hole transport). It is better to form layer A) and to form another hole transport layer containing the organic semiconductor material and the fluorine-containing polymer (hereinafter referred to as hole transport layer B) so as to be in contact with the layer. It seems to be preferable because the interfacial reflection between the light emitting layer 14 and the hole transport layer can be suppressed.

However, in the case of the above configuration, the light incident on the hole transport layer from the light emitting layer 14 is likely to be reflected at the interface between the hole transport layer A and the hole transport layer B.

Therefore, in the configuration of the present invention, the hole transport layer having the lowest refractive index is arranged at the position where it comes into contact with the light emitting layer 14. In such a configuration, reflection at the interface between the light emitting layer 14 and the hole transport layer having the lowest refractive index can be suppressed by controlling the light emitting position in the light emitting layer 14.

In the light emitting layer 14, holes and electrons are recombined to emit photons. At that time, the position where holes and electrons are recombined can be controlled in the thickness direction of the light emitting layer 14 by appropriately selecting the forming material and the thickness of each layer constituting the device. The recombination position of the hole and the electron, that is, the light emitting position can be confirmed by a known method.

In the organic EL element 1, the light emitting position is set at the interface 14a between the light emitting layer 14 and the hole transport layer 13. Therefore, the generated light is emitted toward the light emitting layer 14 and the hole transport layer 13.

At this time, the generated light is incident on the light emitting layer 14 and the hole transport layer 13 without being reflected at the interface 14a. Therefore, it is not necessary to consider the reflection of the light generated at the interface 14a between the light emitting layer 14 and the hole transport layer 13 at the interface between the light emitting layer 14 and the hole transport layer 13.

Therefore, in the hole transport layer 13 of the present embodiment, by setting the light emitting position to the interface 14a between the light emitting layer 14 and the hole transport layer 13, the reflection loss inside the element is reduced and the light extraction efficiency is improved. do.

As described above, in the organic EL element 1 in which the hole transport layer 13 has the above-mentioned configuration, the light extraction efficiency is improved by each of the above-mentioned effects. As a result, the same amount of light emission as that of the conventional organic EL element can be obtained with a smaller input power than that of the conventional organic EL element, and the organic EL element consumes less power.

When the hole transport layer 13 contains a fluorine-containing polymer, the refractive index becomes low, and when the hole transport layer 13 comes into contact with the hole transport layer 13, which has a relatively lower refractive index than the light emitting layer 14, the light extraction efficiency is improved. In order to verify the effect, the result of simulation using Setfos 4.6 (manufactured by Cybernet) will be described. As an example of the organic EL element 1, the element configurations analyzed are: glass (thickness 1 mm) as the substrate 10, ITO (thickness 100 nm) as the anode 11, HAT-CN (thickness 10 nm) as the hole injection layer 12, and the light emitting layer 14. Ir (ppy) ₃ is a light emitting guest, 4,4'-bis (9H-carbazole-9-yl) biphenyl (CBP) (thickness 30 nm) is a light emitting host, TPBi is used as an electron transport layer 15, and LiF is used as an electron injection layer 16. (Thickness 0.8 nm), Al (thickness 100 nm) was used as the cathode 17. Regarding the hole transport layer 13, the configuration in which the low refractive index hole transport layer (refractive index at a wavelength of 550 nm is 1.55) is used as the hole transport layer is described in Examples 1 to 3 and the α-NPD layer (refraction at a wavelength of 550 nm). Comparative Examples 1 to 3 with a hole transport layer having a rate of 1.77), a two-layer structure consisting of an α-NPD layer (thickness 10 nm) and a low refractive index hole transport layer (α-NPD layer is a light emitting layer). Adjacent configurations) were designated as Comparative Examples 4 to 6. Regarding the light emitting layer, the light emitting points in the light emitting layer are located in the middle of the light emitting layer (light emitting point 0.5), on the hole transporting layer side (light emitting point 0.1), and on the electron transporting layer side (light emitting point 0.9). Three conditions were set, and the film thickness of the electron transport layer 15 and the film thickness of the hole transport layer 13 were swept at intervals of 5 nm in the range of 10 nm to 100 nm, and the conditions for maximizing the light extraction efficiency were calculated. The results of the analysis are shown in Table 1.

In Comparative Examples 1 to 3 in Table 1, the light extraction efficiency was 25% regardless of the light emitting point of the light emitting layer, but in Examples 1 to 3, the light extraction efficiency was 28% or more, and the hole transport layer 13 was used. It was confirmed that the light extraction efficiency was improved by lowering the refractive index. Further, when Examples 1 to 3 and Comparative Examples 4 to 6 are compared under the same conditions of the light emitting points of the light emitting layer, the light extraction efficiency is higher in Examples 1 to 3 and the low refractive index hole transport layer is obtained. It was confirmed that the light is adjacent to the light emitting layer to improve the light extraction efficiency.

Further, in the organic EL element 1 having the hole transport layer 13 having the above configuration, the input power is reduced as described above. Therefore, the organic EL element 1 is less likely to deteriorate and has a longer life.

According to the organic EL element 1 having the above configuration, the external quantum efficiency is improved, the power consumption is low, and the life is extended.

[Second Embodiment]
FIG. 2 is a schematic cross-sectional view showing the organic EL element 2 according to the second embodiment of the present invention, and is a diagram corresponding to FIG. 1. Therefore, the components common to the first embodiment in the present embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The organic EL element 2 has a structure in which a substrate 20, an anode 21, a hole injection layer 12, a hole transport layer 13, a light emitting layer 14, an electron transport layer 15, an electron injection layer 16, and a cathode 27 are laminated in this order. There is. The organic EL element 2 of the present embodiment employs a top emission method in which the light L generated in the light emitting layer 14 is emitted to the outside via the cathode 27.

The substrate 20 may or may not have light transmission. As the material for forming the substrate 20, an inorganic substance such as glass, quartz glass, or silicon nitride, or an organic polymer (resin) such as an acrylic resin or a polycarbonate resin can be used. Further, if the insulating property of the surface is ensured, a metal material can be adopted as the forming material of the substrate 20.

The anode 21 is formed on the substrate 20 and supplies holes to the hole transport layer 13. Further, the anode 21 has a light reflectivity that reflects the light emitted from the light emitting layer 14. As the material for forming the anode 21, a conductive metal oxide having light transmittance such as ITO and IZO can be used. Further, in order to impart light reflectivity to the anode 21, a reflective film made of a metal material is provided on the substrate 20 side of the anode 21. That is, the anode 21 has a laminated structure of a layer made of a conductive metal oxide as a forming material and a reflective film.

Further, silver may be used as the material for forming the anode 21.

The cathode 27 is formed in contact with the electron injection layer 16. The cathode 27 is a semi-transmissive film formed thin enough to reflect a part of the light emitted from the light emitting layer 14 as a whole and pass through the rest. Examples of the material for forming the cathode 27 include an MgAg electrode and an Al electrode.

The thickness of the cathode 27 is not particularly limited, but is preferably 5 to 30 nm. The thickness of the cathode 27 is, for example, 5 nm.

(Microcavity structure)
In the organic EL element 1 of the present embodiment, the anode 11 and the cathode 17 form an optical resonance structure (microcavity) in which light is resonated between the anode 11 and the cathode 17. The light generated in the light emitting layer 14 is repeatedly reflected between the anode 11 and the cathode 17, and the light having a wavelength matching the optical path length between the anode 11 and the cathode 17 is resonated and amplified. On the other hand, light having a wavelength that does not match the optical path length between the anode 11 and the cathode 17 is attenuated.
The "optical path length" referred to here is calculated using the wavelength of the desired light emitted to the outside of the element and the refractive index of each layer at the desired wavelength of the light.

The optical path length between the anode 11 and the cathode 17 is set to, for example, an integral multiple of the center wavelength of the light L generated in the light emitting layer 14. In this case, the light L emitted by the light emitting layer 14 is amplified as it is closer to the center wavelength, attenuated as it is farther from the center wavelength, and emitted to the outside of the organic EL element 1. In this way, the light L emitted from the organic EL element 1 has a narrow half-value width of the emission spectrum and improved color purity.

The microcavity structure utilizes resonance due to fixed-end reflection with the cathode and anode at both ends. Therefore, "the optical path length from the light emitting position to the anode is an integral multiple of 1/4 of the wavelength λ of the desired light emitted to the outside of the element", and "the optical path length from the light emitting position to the cathode is outside the element". If it is "an integral multiple of 1/4 of the wavelength λ of the desired light emitted into the", the desired microcavity structure can be formed.

Similar to the organic EL element 1 shown in the first embodiment, the organic EL element 2 having such a configuration also has a lower refractive index than the case where the hole transport layer 13 does not contain the fluorine-containing polymer. By setting this, the light extraction efficiency can be improved.

Further, since the hole transport layer 13 has a lower refractive index than the layer using only the organic semiconductor material, the optical path length inside the device is adjusted by adjusting the film thickness of the hole transport layer 13. Cheap.

That is, even if the film thickness of the hole transport layer 13 deviates from the target value, the film thickness inside the device is different from that in the layer having a relatively high refractive index using only the organic semiconductor material. The effect on the optical path length is small. Therefore, in the organic EL device 1 having the hole transport layer 13 described above, it is easy to control the optical path length inside the device, and it is easy to improve the color purity of the light emitted by the microcavity structure described above.

Further, since the light emitting layer 14 and the hole transport layer 13 having a relatively lower refractive index than the light emitting layer 14 are in contact with each other, the reflection loss inside the element is reduced and the light extraction efficiency is improved.

The organic EL element 2 having the above configuration also improves the external quantum efficiency, consumes less power, and has a longer life.

When the hole transport layer 13 contains a fluorine-containing polymer, the refractive index becomes low, and when the hole transport layer 13 comes into contact with the hole transport layer 13, which has a relatively lower refractive index than the light emitting layer 14, the light extraction efficiency is improved. In order to verify the effect, the result of simulation using Setfos 4.6 (manufactured by Cybernet) will be described. As an example of the organic EL element 2, the element configuration to be analyzed is glass (thickness 1 mm) as the substrate 10, Ag (thickness 100 nm) as the anode 11, HAT-CN (thickness 5 nm) as the hole injection layer 12, and the light emitting layer 14. Ir (ppy) ₃ was a light emitting guest, CBP (thickness 20 nm) was a light emitting host, electron transport layer 15 was Alq ₃ , electron injection layer 16 was LiF (thickness 0.8 nm), and cathode 17 was Al (thickness 10 nm). .. Regarding the hole transport layer 13, the configuration in which the low refractive index hole transport layer (refractive index at a wavelength of 550 nm is 1.56) is used as the hole transport layer is described in Examples 4 to 9, the α-NPD layer (refraction at a wavelength of 550 nm). Comparative Examples 7 to 12 with a hole transport layer having a rate of 1.77), a two-layer structure consisting of an α-NPD layer (thickness 10 nm) and a low refractive index hole transport layer (α-NPD layer is a light emitting layer). (Adjacent configurations) were designated as Comparative Examples 13 to 18. Regarding the light emitting layer, the light emitting points in the light emitting layer are located in the middle of the light emitting layer (light emitting point 0.5), on the hole transporting layer side (light emitting point 0.9), and on the electron transporting layer side (light emitting point 0.1). Three conditions were set, and the film thickness of the electron transport layer 15 was swept at intervals of 30 nm in the range of 50 nm to 230 nm, and the film thickness of the hole transport layer 13 was swept at intervals of 30 nm in the range of 10 nm to 280 nm. The conditions for maximizing the light extraction efficiency on the thin film side (primary resonance) and the thick film side (secondary resonance) were calculated. The results of the analysis are shown in Table 2.

Comparing Examples 4, 5 and Comparative Examples 7, 8, 13, and 14 in which the light emitting point is in the middle of the light emitting layer (light emitting point 0.5) in Table 2, the light emitting layer and the low refractive index hole transport layer are adjacent to each other. It was confirmed that the light extraction efficiency of Examples 4 and 5 was high. Further, even when compared in Examples 6 and 7 and Comparative Examples 9, 10, 15 and 16 in which the light emitting point is on the hole transporting layer side of the light emitting layer (light emitting point 0.9), the light emitting layer and the low refractive index are positive. It was confirmed that the light extraction efficiency of Examples 6 and 7 adjacent to the hole transport layer was high. Further, even when compared in Examples 8 and 9 and Comparative Examples 11, 12, 17 and 18 in which the light emitting point is on the electron transporting layer side (light emitting point 0.1), the light emitting layer and the low refractive index hole transporting layer are still present. It was confirmed that the light extraction efficiency of the adjacent Examples 8 and 9 was slightly higher.

[Third Embodiment]
FIG. 3 is an explanatory diagram of the organic EL element 3 according to the third embodiment of the present invention, and is an enlarged view for explaining in detail the hole transport layer 33 included in the organic EL element 3. Further, the organic EL element 3 is of the bottom emission method as in the organic EL element 1 of the first embodiment.

The organic EL element 3 has a hole transport layer 33 sandwiched between the hole injection layer 12 and the light emitting layer 14.

The refractive index of the hole transport layer 33 continuously changes and gradually increases from the light emitting layer 14 toward the hole injection layer 12 side (anode 11 side). In the figure, the refractive index of the hole transport layer 33 is represented by the shade of color of the hole transport layer 33. The darkly colored portion of the hole transport layer 33 indicates a high refractive index, and the lightly colored portion of the hole transport layer 33 indicates a low refractive index.

Here, when the change in the refractive index is "continuous", it means that the boundary where the refractive index is different cannot be detected in the hole transport layer 33. For example, when two hole transport layers having different refractive indexes are laminated, a boundary having different refractive indexes can be detected at the interface between the two layers, so that the above-mentioned "continuous" does not apply.

Further, when the refractive index is "gradually increased", it means that the refractive index is "gradually increased". If the refractive index does not decrease, a region in which the refractive index does not change in the thickness direction of the hole transport layer 33 may be included.

The hole transport layer 33 has a low refractive index of the region 33x near the surface 33a on the light emitting layer 14 side, and a high refractive index of the region 33z near the surface 33a on the hole injection layer 12 side. The region 33y near the center in the thickness direction of the hole transport layer 33 has, for example, a refractive index about halfway between the regions 33x and the regions 33z.

It is preferable that the difference in refractive index at the interface between the hole injection layer 12 and the hole transport layer 33 is small. The smaller the difference in refractive index, the more the loss due to reflection (intra-film propagation) can be reduced.

In the refractive index distribution of the hole transport layer 33, the lowest refractive index is preferably 1.60 or less, and more preferably 1.55 or less in the wavelength range of 450 nm to 800 nm. When the refractive index of the hole transport layer 33 is 1.60 or less, the light extraction efficiency of the organic EL element 3 is improved. On the other hand, the lowest refractive index in the hole transport layer 33 is preferably 1.3 or more, and more preferably 1.4 or more, from the viewpoint of ensuring conductivity.

Further, the position where the refractive index is the lowest in the hole transport layer 33 is the position where the light extraction efficiency is the highest, the position where the color purity is the highest, or the optimum position in consideration of the balance between the two by optical calculation. It is preferable to adjust to.

In the organic EL element 3 having the hole transport layer 33 having the above configuration, in addition to the effect of the organic EL element 1 of the first embodiment, light is reflected at the interface between the hole injection layer 12 and the hole transport layer 33. , And reflection inside the hole transport layer 33 can be suppressed.

When light is incident on the interface between two layers with different refractive indexes, part of the light is refracted and the rest is reflected. Further, when light is incident from a layer having a large refractive index toward a layer having a small refractive index, total reflection may occur at the interface between the two layers depending on the angle of incidence.

When the light generated in the light emitting layer 14 is reflected at the interface between the hole injection layer 12 and the hole transport layer 33, the probability that the reflected light is attenuated inside the organic EL element increases. As a result, the light extraction efficiency is lowered.

Reflection at such an interface is more likely to occur as the difference in refractive index between the two layers in contact with each other is larger. Therefore, in order to suppress interfacial reflection, it is preferable to reduce the difference in refractive index between layers.

In this respect, the organic EL element 3 of the present embodiment is designed so that the difference in refractive index at the interface between the hole injection layer 12 and the hole transport layer 33 is small, and reflection at the interface is suppressed. ..

Further, in order to reduce the difference in the refractive index at the interface between the hole injection layer 12 and the hole transport layer 33, the refractive index changes continuously inside the hole transport layer 33, and the change in the refractive index becomes discontinuous. It has a structure that does not generate an interface, and reflection inside the hole transport layer 33 is suppressed.

Therefore, it is possible to suppress the internal reflection of the light emitted from the light emitting layer 14 and improve the light extraction efficiency.

4A to 4C are schematic views showing a process of manufacturing the hole transport layer 33 of the organic EL element 3 described above.

FIG. 4A shows how the region 33z of the hole transport layer 33 is formed.
First, as shown in FIG. 4A, the substrate 10 on which the anode 11 and the hole injection layer 12 are formed is prepared. Such a substrate 10 is installed in the chamber 100 of the vacuum vapor deposition apparatus, and the organic semiconductor material 101a and the fluorine-containing polymer 102a are supplied from the vapor deposition source 101 of the organic semiconductor material and the vapor deposition source 102 of the fluorine-containing polymer. Co-deposited. In the figure, the amount of each of the organic semiconductor material 101a and the fluorine-containing polymer 102a is shown by the amount of the figure shown as the organic semiconductor material 101a and the fluorine-containing polymer 102a. By reducing the vapor deposition ratio of the fluorine-containing polymer 102a, the refractive index of the obtained film 331 becomes high.

FIG. 4B shows how the region 33y of the hole transport layer 33 is formed.
As shown in FIG. 4B, at least one of the heating temperature of the vapor deposition sources 101 and 102 or the opening of the lid of the vapor deposition sources 101 and 102 is adjusted, and the vapor deposition ratio of the semiconductor material and the fluorine-containing polymer is changed. Both materials are co-deposited. Specifically, as compared with the step of forming the region 33z, the vapor deposition rate of the fluorine-containing polymer is increased and the vapor deposition rate of the organic semiconductor material is decreased. As a result, the content of the fluorine-containing polymer is increased as compared with FIG. 4A, and the refractive index of the obtained film 332 is gradually lowered.

FIG. 4C shows how the region 33x of the hole transport layer 33 is formed.
As shown in FIG. 4C, as compared with the step of forming the region 33y, for example, the vapor deposition rate of the fluorine-containing polymer is lowered and the vapor deposition rate of the organic semiconductor material is increased. As a result, the hole transport layer 33 in which the content of the fluorine-containing polymer is higher than that in FIG. 4B and the refractive index is further lowered in the vicinity of the surface is obtained.

In forming the hole transport layer 33, the change control of the vapor deposition rate shown in FIGS. 4A to 4C described above is continuously controlled so that the refractive index change of the obtained hole transport layer 33 is continuous. conduct.

5A and 5B are explanatory views illustrating the change in the refractive index of the hole transport layer 33 obtained by the above method. In FIGS. 5A and 5B, the horizontal axis indicates the position of the hole transport layer 33 in the thickness direction. 33a and 33b shown on the horizontal axis represent the surface 33a and the surface 33b of the hole transport layer 33 described above. The vertical axis indicates the refractive index at the position of the hole transport layer in the thickness direction.

In both FIGS. 5A and 5B, the refractive index changes continuously from the surface 33a (light emitting layer 14 side) of the hole transport layer 33 toward the surface 33b (anode 11 side), and the refractive index gradually increases. There is.

As shown in FIG. 5A, the refractive index of the hole transport layer 33 may change linearly from the surface 33a to the surface 33b of the hole transport layer 33. In the following description, the hole transport layer 33 having a refractive index change as shown in FIG. 4A is referred to as a hole transport layer 33α.

In this case, the hole transport layer 33α can be manufactured by increasing the vapor deposition rate of the organic semiconductor material at a constant rate and decreasing the vapor deposition rate of the fluorine-containing polymer at the same rate, and the manufacturing process can be easily controlled. Become.

Further, as shown in FIG. 5B, the refractive index of the hole transport layer 33 gradually increases as it approaches the surface 33a of the hole transport layer 33, and then changes sharply toward the surface 33b. good. In the following description, the hole transport layer 33 having a refractive index change as shown in FIG. 5B is referred to as a hole transport layer 33β.

In this case, assuming that the thickness of the hole transport layer 33β is the same as that of the hole transport layer 33α shown in FIG. 5A, the amount of the fluorine-containing polymer contained in the hole transport layer 33β is the hole transport layer 33α. Will be more than. Therefore, the average refractive index of the entire hole transport layer 33β is smaller than the average refractive index of the entire hole transport layer 33α, and the light extraction efficiency is improved as compared with the hole transport layer 33α.

Further, the refractive index of the hole transport layer 33 may gradually decrease toward the surface 33a of the hole transport layer 33, and then gradually decrease toward the surface 33b.

As described above, in the present embodiment, the hole transport layer 33 in which the refractive index is continuously changed can be easily formed by controlling the vapor deposition rate at the time of co-deposition.

Even in such an organic EL device, in addition to the effects described in the first embodiment and the second embodiment, since the hole transport layer is a single layer, no reflection loss occurs inside the hole transport layer, and light is emitted. Extraction efficiency is improved.

The organic EL element 3 having the above configuration also improves the external quantum efficiency, consumes less power, and has a longer life.

In the present embodiment, the organic EL element 3 has been described as having a bottom emission system, but it can also be applied to a top emission system.

The organic optoelectronic device of the present embodiment described above can be used for an organic optoelectronic device such as an organic EL device, a solar cell, an organic photodiode, and an organic laser.

In particular, the organic photoelectron device of this embodiment is suitably used as an organic EL device. Such an organic EL element can be used for an organic EL device such as an organic EL display and an organic EL lighting. These organic EL devices may be a top emission type or a bottom emission type.

"Measurement of refractive index of charge transport layer"
Using multi-incident angle spectroscopic ellipsometry (manufactured by JA Woolam: M-2000U), the incident angle of light is changed by 5 degrees in the range of 45 to 75 degrees with respect to the film on the silicon substrate. Was done. At each angle, ellipsometry parameters Ψ and Δ were measured at intervals of approximately 1.6 nm in the wavelength range of 450 nm to 800 nm. Using the above measurement data, the dielectric function of the organic semiconductor was subjected to fitting analysis by the Cauchy model, and the film thickness of the charge transport layer and the refractive index of the charge transport layer with respect to light of each wavelength were obtained.

The abbreviations of the monomers, solvents and polymerization initiators used in the production of the following fluorine-containing polymers are as follows.
BVE: Perfluoro (3-butenyl vinyl ether)
TFE: Tetrafluoroethylene PPVE: Perfluoro (n-propyl vinyl ether) (CF ₂ = CFOCF ₂ CF ₂ CF ₃ )
1H-PFH: 1,1,1,2,2,3,3,4,5,5,6,6-tridecafluorohexane IPP: diisopropyl peroxydicarbonate AIBN: azobisisobutyronitrile

<Synthesis of polymer A>
30 g of BVE, 30 g of 1H-PFH, 0.5 g of methanol and 0.44 g of IPP were placed in a glass reactor having an internal volume of 50 ml. After substituting the inside of the system with high-purity nitrogen gas, polymerization was carried out at 40 ° C. for 24 hours. The obtained solution was desolvated under the conditions of 666 Pa (absolute pressure) and 50 ° C. to obtain 28 g of the polymer. The intrinsic viscosity [η] of the obtained polymer was 0.04 dl / g.
Next, the obtained polymer was replaced with ₃ -CF groups of unstable terminal groups with fluorine gas by the method described in paragraph [0040] of JP-A-11-152310 to obtain a polymer A.
The refractive index of the obtained polymer A with respect to light having a wavelength of 600 nm was 1.34, and the intrinsic viscosity [η] was 0.04 dl / g. The Mw of the polymer A is 9,000, Mn is 6,000, Mw / Mn is 1.5, the saturated vapor pressure at 300 ° C. is 0.002 Pa, and the evaporation rate at 300 ° C. is 0.08 g / m ² sec. rice field.

<Synthesis of polymer B>
A stainless steel autoclave having an internal volume of 1006 mL was charged with 152.89 g of PPVE, 805.0 g of AC2000, 2.400 g of methanol, and 1.149 g of AIBN, and was frozen and degassed with liquid nitrogen. After raising the temperature to 70 ° C., TFE was introduced until it reached 0.57 MPaG. TFE was continuously supplied and polymerized while keeping the temperature and pressure constant. After 9 hours from the start of the polymerization, the autoclave was cooled to stop the polymerization reaction, and the gas in the system was purged to obtain a solution of the fluorine-containing polymer.
813 g of methanol was added to the solution of the fluorinated polymer and mixed, and the lower layer in which the fluorinated polymer was dispersed was recovered. The obtained dispersion of the fluorinated polymer was dried with warm air at 80 ° C. for 16 hours and then vacuum dried at 100 ° C. for 16 hours to obtain 18.92 g of the fluorinated polymer.
The composition of the fluorine-containing polymer was PPVE: TFE = 14: 86 mol%.
Next, the obtained fluorine-containing polymer was heated in an oven at 330 ° C. for 5 hours, then immersed in methanol and heated in an oven at 75 ° C. for 20 hours to replace unstable terminal groups with methyl ester groups to contain fluorine. Polymer B was obtained. Since Mw and Mn of the fluorine-containing polymer B cannot be measured by the above method, the relationship between the elastic modulus of the polymer B and the temperature is shown in FIG. 8 instead.
The refractive index of the obtained polymer B with respect to light having a wavelength of 600 nm was 1.34, and the evaporation rate at 300 ° C. was 0.04 g / m ² sec.

<Manufacturing of organic EL element A>
As a substrate for manufacturing the organic EL element A, a glass substrate on which ITO (indium tin oxide) was formed into a strip having a width of 2 mm was used. The substrate was ultrasonically cleaned with a neutral detergent, acetone, and isopropanol, and then boiled and washed in isopropanol, and then the deposits on the surface of the ITO film were removed by ozone treatment. This substrate was placed in a vacuum vapor deposition machine and evacuated to a pressure of 10 ^-4 Pa or less, and then HAT-CN was set to 10 nm as the hole injection layer 12, Tris-PCz was set to 30 nm as the hole transport layer 13, and the light emitting layer 14 was used. 3,3'-di (9H-carbazole-9-yl) -1,1'-biphenyl (mCBP) and Ir (ppy) ₃ co-deposited film 30 nm, TPBi 50 nm as electron transport layer 15, electron injection layer LiF was laminated as 16 and Al was 100 nm as the cathode 17, respectively, to obtain an organic EL element A. The co-deposited film of the light emitting layer 14 has a concentration of Ir (ppy) ₃ of 6 wt. The film was formed by controlling the vapor deposition rates of mCBP and Ir (ppy) ₃ so as to be%.

<Manufacturing of organic EL element B>
It was produced in the same manner as the organic EL element A except that a co-deposited film of Tris-PCz and the polymer A was formed as the hole transport layer 13 at a volume ratio of 50:50 at 50 nm.

<Manufacturing of organic EL element C>
It was produced in the same manner as the organic EL element A except that a co-deposited film of Tris-PCz and the polymer B was formed as the hole transport layer 13 at a volume ratio of 50:50 at 50 nm.

[Example 10]
The silicon substrate cut to about 2 cm square was ultrasonically cleaned with a neutral detergent, acetone, and isopropanol, respectively, and then boiled and washed in isopropanol, and then the deposits on the surface of the substrate were removed by ozone treatment. Each of these substrates is placed in a vacuum vapor deposition machine, evacuated to a pressure of 10 ^-4 Pa or less, and then the polymer A and Tris-PCz are subjected to resistance heating in the vacuum vapor deposition machine so that the volume ratio is 50:50. Then, a hole transport layer having a thickness of about 100 nm was produced on the substrate by co-depositing. The refractive index of the obtained hole transport layer with respect to light having a wavelength of 600 nm was 1.55.

[Example 11]
A hole transport layer was formed in the same manner as in Example 10 except that the polymer B was used instead of the polymer A. The refractive index of the obtained hole transport layer with respect to light having a wavelength of 600 nm was 1.55.

[Comparative Example 19]
The hole transport layer was formed in the same manner as in Example 10 except that only Tris-PCz was formed as the hole transport layer at about 100 nm. The refractive index of the obtained hole transport layer with respect to light having a wavelength of 600 nm was 1.84.

From Example 10, Example 11 and Comparative Example 19, Tris-PCz and the fluorine-containing polymer are co-deposited so that the volume ratio is 50:50, so that the refractive index is 1.84 to 1.55. It was confirmed that it decreased to.

[Example 12]
When a voltage was applied to the organic EL element B and the current efficiency and power efficiency were measured at a constant current of 0.2 mA / cm ² , the current efficiency was 72 cd / A and the power efficiency was 51 lm / W.

[Example 13]
When a voltage was applied to the organic EL element C and the current efficiency and power efficiency were measured at a constant current of 0.2 mA / cm ² , the current efficiency was 73 cd / A and the power efficiency was 53 lm / W.

[Comparative Example 20]
When a voltage was applied to the organic EL element A and the current efficiency and power efficiency were measured at a constant current of 0.2 mA / cm ² , the current efficiency was 64 cd / A and the power efficiency was 43 lm / W.

From the results of Examples 10 to 13 and Comparative Examples 19 to 20, the hole transport layer in which the hole transport layer 13 containing the fluorine-containing polymer was used and the current efficiency and power efficiency of the device did not contain the fluorine-containing polymer was obtained. It was shown that the current efficiency and power efficiency were higher than those of the elements used. It is considered that this efficiency improvement is due to the fact that the hole transport layer 13 having a low refractive index is adjacent to the light emitting layer 14 and the light extraction efficiency is improved.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. The various shapes and combinations of the constituent members shown in the above-mentioned example are examples, and can be variously changed based on design requirements and the like within a range not deviating from the gist of the present invention.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2017-161642 filed on August 24, 2018 are cited here as the disclosure of the specification of the present invention. It is something to incorporate.

10, 20 ... Substrate, 11,21 ... Anode, 12 ... Hole injection layer, 13 ... Hole transport layer, 14 ... Light emitting layer, 15 ... Electron transport layer, 16 ... Electron injection layer, 17, 27 ... Cathode, 101a ... Organic semiconductor material, 102a ... Fluorine-containing polymer, L ... Light

Claims (12)

With the board
With the anode provided on the substrate,
The cathode facing the anode and
A light emitting layer arranged between the anode and the cathode,
A hole transport layer provided in contact with the light emitting layer between the light emitting layer and the anode is provided.
The hole transport layer contains an organic semiconductor material and a fluorine-containing polymer, and contains.
The fluorine-containing polymer is present on the surface of the hole transport layer in contact with the light emitting layer.
The evaporation rate at 300 ° C. of the fluorine-containing polymer at a vacuum degree of 1 × 10 ^-3 Pa is 0.01 g / m ² sec or more.
The glass transition point of the fluorine-containing polymer is 60 ° C. or higher, and the temperature is 60 ° C. or higher.
The fluorine-containing polymer is a fluorine-containing polymer having no aliphatic ring in the main chain and having a unit derived from a fluoroolefin, or a fluorine-containing polymer having an aliphatic ring structure in the main chain.
The fluoropolymer having no aliphatic ring in the main chain and having a unit derived from fluoroolefin is a tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, and the like. Group consisting of tetrafluoroethylene / perfluoro (alkyl vinyl ether) / hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylfluoride, polychlorotrifluoroethylene, and ethylene / chlorotrifluoroethylene copolymer. An organic photoelectron element , which is at least one selected from the above . The organic photoelectron device according to claim 1, further comprising a hole injection layer arranged between the hole transport layer and the anode and containing a semiconductor material and a fluorine-containing polymer. The organic photoelectron device according to claim 1 or 2, wherein the hole transport layer has a refractive index continuously increasing gradually from the light emitting layer toward the anode. Further having a functional layer arranged between the cathode and the light emitting layer,
The organic photoelectronic device according to any one of claims 1 to 3, wherein the functional layer has at least one of an electron transport layer and an electron injection layer, and includes a semiconductor material and a fluorine-containing polymer. The organic photoelectron device according to any one of claims 1 to 4, wherein the hole transport layer provided in contact with the light emitting layer has a refractive index of 1.60 or less in a wavelength range of 450 nm to 800 nm. The volume ratio of the content (A) of the fluorine-containing polymer to the content (B) of the organic semiconductor material in the hole transport layer is (A) :( B) = 70: 30 to 5:95. The organic photoelectron device according to any one of claims 1 to 5. The organic photoelectron device according to any one of claims 1 to 6, wherein the fluorine-containing polymer has a refractive index of 1.5 or less in a wavelength range of 450 nm to 800 nm. The organic photoelectronic device according to any one of claims 1 to 7 , wherein the fluorine-containing polymer has a weight average molecular weight of 1,500 to 50,000. The organic photoelectron element according to any one of claims 1 to 8 , wherein the fluorine-containing polymer is a perfluoropolymer having an aliphatic ring structure in the main chain. The organic photoelectronic device according to claim 9 , wherein the perfluoropolymer is polyperfluoro (3-butenyl vinyl ether). The organic photoelectronic device according to claim 10 , wherein the polyperfluoro (3-butenyl vinyl ether) has an intrinsic viscosity of 0.01 to 0.14 dl / g. The organic photoelectron device according to any one of claims 1 to 11 , wherein the organic photoelectronic device is an organic EL device.

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